Spool valves



Dec. 25, 1956 Filed 001;. 30. 1952 J. H. DRENNEN SPOOL VALVES 3 Sheets-Sheet 1 INVENTOR John It Drennfn Dec. 25, 1956 J. H. DRENNEN SPOOL VALVES 3 Sheets-Sheet 2 Filed Oct. 30, 1952 J. H- DRENNEN Dec. 25, 1956 SPOOL VALVES 3 Sheets-Shet 3 Filed Oct. 30. 1952 m mm United States Patent 2,775,260 sPooL VALVES John H. .Drennen, Girard,l1io, assignor to ThegCommenial-Shearing & Stamping (30., Youngstown, Ohio, a corporation of Ohio ApplicationDctober 30, 1952, Serial No. 317,670 16 Claims. or. 137- 621) This invention relates to valves with axially shift'able spool valve elements, and more particularly to means tently to the cylinder so that the operator can accurately control and adjust the position of the lifting fork while picking up and stacking packages. With conventional spool valves there is an intermediate position of the spool between neutraland drive positions in which the lineto the cylinder iseither momentarily opento the dischargeline from the valve, so that the"cylinder"e'mp ties under load and the fork sagsfor else the spool blocks both the pump supply line and the cylinder supply line "from the discharge outlet and consequently imposes unnecessary strain on the pilinpas the back pressure I'builds up to the relatively high pressure" required to open the relief valve in the pump supply line. Both alterna- Yt ive s are undesirable but cannotbe entirely avoided with conventional forms of spool valves.

In accordance with my inventionit is possible td shift the spool from neutral to drive positions withoutany finterrnediate period in which the pump supply line is blocked or in which the connected cylinder is memenr tarilyfree todischarge in response to loadpress'ures on l the piston cylinder. In the present preferred embodiment {of myirivention a sleeve is'mounted on the spool for ;:sliding movement along the spool and also along the valve The spool and the sleeve havea compound nrove- Ement and'provide a two-stage change of valving eonmesons with the sleeve slidable on the spool in "re- :sponse to pressures in the pump line to switch the'flow lbeforethefbackpressures become excessive. The sleeve operates automatically with resilient biasing'means moving itin one direction and fluid pressures overcoming thepreesure of the resilient biasing means tomove itin the other direction. Ifu-rther provide a generally oval opening in thespool for switching cylinder return flow to the low-pressure tank returnlinein a gradual manner which avoidssudden drop of a load supported by a'sin'gle- "ecting cylinder, and coordinates the relief ofone end of a double-acting cylinder as the spool-sleeve motion; against the sleeve spring starts fiow' of pressure fluid into the other end of the cylinder.

Other features, objects and advantages of rny invention .will become. apparent from the following detailed description and in the accompanying drawings, in which! Figure 1 is a partly broken-away and sectioned view of a multiplevalve embodying my invention;

Figure Z isan end view from the right of Figure 1,

i11 "the valve in locked neutral position;

"showing details in dottedlines of the double acting spool.

2,775,260 Patented Dec. 25, 1956 2 Figure B-is a section on the line IIIIII in Figure 1, showing the double-acting valve element in a position to relieve one connected cylinder line while supplying fluid under pressure to the other;

Figure 4 is an enlarged view of the section of the valve shown in Figure 1 with the double-acting float spool,

with the spool in locked neutral position;

Figure 5 corresponds to Figure 4 but shows the spool shifted partly from locked neutral position to its posi* tion in which one connected cylinderreceives fluid under "pressure while the other discharges; and

Figure 6 corresponds to Figure 5 but shows the spool in final position for supplying fluid under pressure to one cylinder while receiving discharge from the other. *Referring now more particularly to the drawings and initiallyrto Figure 1, there is provided a multiple valve 10 -connected to a hydraulic pump (not shown) through a line 11 and connected to a tank (not shown) through a line-12. The line 11 feeds into a passage 13 throughan inletend section 14, and the line 12 is connected to a 3 pair of: passages 15 and 16 in the outlet end section 17 of the valve 10. Three valve sections 18, 19 and20 are mounted in series between the end sections 14 and 17. The bodies 21, 22 and .23 of the-valve sections 1820 have-aligned passages 24, 25 and 26 therethrough connecting the passages Band 15 of the end bodysections 14 and 17, and have a second series of aligned passages 27, Mind 29 connected to discharge fluid t0 passagelfi of the outlet end section 17. The inlet end section 14 has a passage therethrough from its passage 13 to the :passage 27 of valve section 18 controlled by a relief valve 30 which opens only when back pressure on the supply -line 11 exceeds a predetermined maximum pressure. Spools *3133 are slidable'in the bodies 21-23 to control flow therethrough. The body 21 has a port 34 adapted to be connected to a single-acting cylinder, and

the spool 31 is shiftable to one position to direct fluid entering the passage 24 to the port34, and to another :position to by-pass fluidentering the passage 24 to the passage 25 while permitting a return flow through the port 34' to the passage 27 for exhausting the connecting cylinder. The body 22 has ports 35 and 36 adapted to be connected to a double-acting cylinder, and the spool 32 is shiftable to one position to direct fluid entering the passage 25 to the port 35 while permitting return flow through port 36 to passage 28, to a second position to 1 direct fluid entering the passage 25 to the port 36 while permitting return flow through the port 35 to passage 28,

and to a third position to by-pass'fluid entering the passage 25 to the passage 26 while blocking any flow through the ports 35' and36. The body 23 has ports 37 and 38 adapted to be connected to opposite. ends of a doubleacti-ng cylinder, and the spool 33 is shiftable to one position to direct fluid entering the passage 26 to the port '38 while allowing a return flow through the port 37 to the passage 29, to a second position to direct flow through 'the passage 26 to the port 37 while permitting a return flow through the port 38 to the passage 29, to a third position to by-pass fluid entering the passage 26 to the passage 15 while blocking any flow through the ports 37 and 38,-and to a fourth position to by-pass fluid entering the passage 26 to the passage 15 while connecting both the ports 37 and 38 to the passage 29. Whenthe spool 31 is inits second position and the spools 32 and33 are in either of their last two positions flow fromthe "line 11 isby-passed through the passages 13, 24, 25, 26 r and 15 to the return line 12. Preferably only one'spool at a time is positioned to supply fluid under pressure to a cylinder. The valve structure and operation as thus far "described is conventional.

Referring now inmore detail-to the valve section20 (Figures 26), the body section 23 has a passage therethrough with a series of cylindrical surfaces 39--45 slidably engageable with the spool 33 and a series of annular chambers 46--51 therebetween extending around and opening into the spool passage. The chamber 50 is connected to the inlet end 26a of the passage 26 which receives fluid under pressure from the passage 25 of the preceding body section 19, and the chambers 50 and 46 are connected by a conduit 50a extending through the body 23 (Figures 2 and 3). The chamber 50 is connected by the passage through the cylindrical body surface 44 to the chamber 51, which is connected through the outlet end 26b of the passage26 to the passage 15 of the end section 17. The chamber 48 is part of the discharge passage 29, and the chambers 47 and 49 are connected to the respective ports 37 and 38. v

The spool 33 has a central cylindrical portion 52 and lends 52a (Figure and 52b (Figure 4) of reduced diameter projecting integrally from opposite ends of the central portion 52. A helical spring and a sleeve 54 are slidably mounted on the end 52a between the central portion 52 and a sleeve 55 secured to the end 52a by a pin 57. A forked extension 56 of sleeve 55 is suitably linked to a handle 58 for moving the spool 33 in the body section 23. A resilient O-ring 59 (Figure 4, omitted in Figures 5 and 6) seals the sliding connection between the outer end of the sleeve 55 and the outer end of the body 23. The inner end of the sleeve 55 has a flange 60 of the same diameter as spool portion 52 and alternately slidable along the cylindrical body surfaces 44 and 45, and

the sleeve 55 has a circumferential'groove 61 to the left of the flange 60 for permitting flow of fluid from the inlet end 26a of the passage 26 to its outlet end 26b when the flange 60 is to the right of the cylindrical body surface 44. The sleeve 54 has a flanged portion 62 with a diameter about one thousandths of an inch less than the diameter of the spool portion 52 and normally spaced by the spring adjacent end of the spool portion 52 are slidable into the cylindrical body surface 44 to control flow from the inlet end 26a to the outlet end 26b of the passage 26, into the cylindrical body surface 43 to control flow from the passage 26 to the chamber 49 and port 38, and into the cylindrical body surface 42 to control flow from the chamber 49 to the chamber 48 and discharge passage 29. In

. all positions of the spool 33 and of the sleeve flange 62 the inlet passage 26a is connected through the passage 500 with the chamber 46. Flow from the latter chamber is controlled by the other end of the spool 33, as hereinafter described.

A generally oval opening 64 extends transversely through the spool portion 52 for alternately connecting the chambers 49 and 47 with the chamber 48 and discharge passage 29. The axial length of the opening 64 is equal to the width of the chamber 48, and when the opening 64 is centered in the chamber 48 both of the chambers 49 and 47 are blocked by the solid ends of the spool portion 52 within the cylindrical body surfaces 41 and 42 adjacent the opposite ends of the opening 64 (Figure 4).

A spring 65, sleeve 66 and rings 67 and 68 are mounted on the spool end 52b, the spring 65 being received in annular counterbores in the adjacent ends of sleeve 66 and spool portion 52 in the same fashion as spring 53 in the counterbores in sleeve 54 and the other end of spool portion 52. The rings 67 and 68 are pinned to the spool end 52b, and the inner surface of the ring 67 is sealed to the spool end 52b by a resilient Q-lll1g 70 while its outer surface slidably engages the cylindrical body surface 39.

compression spring 72 therebetween.

Leakage into the interior of the cap 73 is returned to the discharge passage 29 under control of a relief valve 79 (shown in Figure 4 and omitted in Figures 5 and 6).

The sleeve 66 has a flange of a diameter about one thousandths of an inch less than the diameter of the spool portion 52. The flange 80 is adapted to abut the spool portion 52 but is normally spaced therefrom by the spring 65 with the other end of the sleeve 66 abutting the ring 67. The flange 80 and adjacent end of the spool portion 52 are slidable into the adjacent cylindrical body surfaces 40 and 41 to control flow between chamber 47 and chambers 46 and 48, respectively.

The spool 33 has four operating positions. When in the position shown in Figure 4 with the detent balls 71 in the groove 76 fluid under pressure is by-passed from the inlet end 2611 to the outlet end 26b of the passage 26 through the open space between the unflanged portion of the sleeve 54 and the cylindrical body surface 44. Flow between the chambers 47 and 49 respectively and the discharge passage 29 is blocked by the solid parts of the spool portion 52 adjacent the opposite ends of the transverse opening 64, and flow of fluid under pressure from the conduit 50a and chamber 46 is blocked by the sleeve flange 80 and adjacent end of the spool portion 52 within the cylindrical body surface 40. The spool 33 is therefore in a locked neutral position with all flow through the chambers 47 and 49 and the connected ports 37 and 38 blocked. Pressures are substantially balanced on both ends of the sleeves 54 and 66 and consequently in this position the springs 53 and 65 act to space these sleeves from the adjacent ends of the spool portion 52.

When shifting the spool 33 to move the detent balls 71 from groove 76 to groove 77, as shown in Figures 46, the fluid conditions just described continue until the left end of the spool portion 52 passes out of the cylindrical body surface 43, thereby opening the annular space between the sleeve flange 62 and the adjacent end of the spool portion 52 to the chamber 49. The fluid pressure in the passage 26 thereupon begins to urge the sleeve 54 toward the spool portion 52 with increasing force as the flange 60 approaches the cylindrical body surface 44. Before the flange 60 reaches the cylindrical body surface 44 the rounded right end of the spool opening 64 enters the chamber 47 and gradually opens the chamber 47 through the opening 64 into the chamber 48 and discharge passage 29. vThis relieves return flow pressure in the chamber 47 as the flange 60 finally reaches the cylindrical body surface 44 (assuming ports 37 and 38 to be connected to opposite ends of a double-acting cylinder), and

. just before this happens the pressure in passage 26 shifts the sleeve 54 against the adjacent end of the spool portion 52 and thereby moves the sleeve flange 62 out of the cylindrical body surface 43 and connects the inlet end 26a of passage 26 with the chamber 49. There is no intermediate period when flow from the inlet 26a is not able to flow either out through the outlet 26b or into the chamber 49 to supply fluid under pressure to the port 38. Moreover, the spring pressure on sleeve 54 insures a gradually increasing flow into the chamber 49 so that the 7 piston of a cylinder connected to port 38 will not be moved suddenly in case it should not be under load, and the rounded end of the opening 64 also contributes to this effect. Flow from the inlet 26a to the chamber 49 continues as the spool 33 completes its movement to the right to carry the detent balls 71 into the groove 77. Before the balls 71 enter the groove 77 the left end of the sleeve flange 62 passes out of the cylindrical body surface 43 and the resultant equalized pressure on the sleeve-54.

permits the spring 53 to shift the sleeve 54 back. into its this movement the rightend of the spool portion 52 blocks flowkfrom the chamber 46 to the chamber 47andthe sleeve flange 80 passes out of the cylindricalbody surface 40::to, a position adjacent the cylindrical bodysurface 39, without any unbalance of pressures on the sleeve 66 tending to shift it relative to the spool33.

Furthermovement of the spool 33 to the right carries the detent balls 71 from groove 77 to grove78. Just before the flange 60 leaves the cylindrical body surface 44the left end of the spool portion 52 enters the chamber 48 :and fluid pressure in thechamber 49 forces the sleeve 54 against the spool portion 52. As the flange 60 continues to a position between and separated from the cylindrical body surfaces 43 and 44 the flow through the inlet end 26a of the passage 26 is divided, some of it passing to the outlet 26b and the balance flowing to the chamber 49;" As the flange 60 enters the cylindrical body surface 43 the'sleeve flange 62 is forced by fluid pressure (assuming the cylinder connected to chamber 49 to be under load), toward spool portion 52 to open a passage from the chamber 49 to the chamber 48, andthe pressure ofthe spring 53 tends to close such passage initially until the sleeve flange 62is well clear of cylindrical body surface, 42andsleeve 54 is again in abutting relation with flange 60. During the entire period of movement ofthe detentballs 71 from the groove 77 to the groove 78 the spool passage 64 connects the chamber 47 with chamber 48. At the end of the movement the flow through the inlet 26a is entirely by-passedthrough the outlet 26b, and

the chambers 47 and 49 are both connected withthe discharge passage 29 to free the cylinder connected to the ports 137and 38 from any fluid pressures or resistances, thus connecting the cylinder piston forfree-floatingmovement.

During return leftward movement of the spool 33 to carry the detent balls 71 from the groove 78' to the groove 77 the sleeve flange 62 enters the cylindrical body surface without any movement toward the adjacent end of the spool portion 52, unless there should be enough back pressure in the chamber 49 to produce such a movement,

and'is then pushed against the spool portion 52 by fluid pressure as thefiange'60 moves to the left of cylindrical body surface 43 to-start flow from inlet 26a to chamber 49. it At the end of the movement to groove 77 the spool portion 52 enters cylindrical body surface 42 and the spring 53 pushes sleeve 54 back into abutting relation with flange 60 as: leakage equalizes fluid pressure on opposite sides of sleeve flange 62, and the flange 60 enterscylindrical body surface 44 to block flow from inlet 26a-to outlet 2611. During this whole period of movement the-spool opening 64 continues to connect the chamber 47 with the chamber 48 and the right end of spool portion;52 is in cylindrical body surface 40 to block flow between chambers 46 and 47, with the sleeve 66 remaining in its position abutting ring 67.

Continued leftward movement of spool 33 carries the detentballs 71 from the groove 77 to the groove 76. The sleeve 54 is forced byfluid pressure toward the spool end 52 as it approaches the cylindrical body surface 43 to continue to allow flow from the inlet 26a to the chamber 49until the flange 60 passes to the left of the cylindrical body surface 44 and thereby connects the inlet 26a with the outlet26b. As inlet 26a is opened into outlet 26b the back pressure drops and equalizes pressure on sleeve 54 to allow it to return to abutting relation with the flange 60 before the left end of the spool portion 52 passes into the cylindrical body surface 43 near the end of-the movement to block flow from inlet 26a to chamber 49. i As the flange 60, passes to the left of cylindrical body surface 44 ,tostart flow to outlet 26b and sleeve flange 62 is choking fiowto chamber 49, the right; end of spool opening 64lprogressivelypcuts off the corresponding return flow, from chamber 47 todischarge passage 29 and cuts it off Hentirelytas flowwtochamber 49 is cut ofi. Throughout all a of this movement the-right end of thespool portion 52 continues to engage the cylindrical body surface to block chamber 46 from chamber 47, and the sleeve 66 remains in its position abutting thering 67.

During finalleftward movement of spool 33 to carry the detent balls 71 from the groove 76 to the groove 75, the left end of the spool portion 52 continuously blocks passage between the passage 26 and chamber 49 and the sleeve 54 continues in abuttingposition against the flange 60; During the initial portion of this movement the inlet 26a discharges through the outlet 26b, and the right end of the spool portion 52 passes to the left of the cylindrical body surface 40, whichcontinues to be occupied by 'the sleeve flange 80-to block passage from the chamber 46 to the chamber 47. As the approach of sleeve flange 62 to cylindrical body surface 44 throttles passagefromthe inlet 26a to the outlet26b to the left end of the spool opening 64 enters the chamber 49 to connect the latter chamber to a progressively larger extent with discharge 1 passage29. In the meanwhile, the throttling of the inlet 26a builds up pressure in the conduit: a and chamber 46 andthis begins to shift the sleeve 66 toward the spool portion 52, thereby moving the sleeve flange 80 out of the cylindrical body surface 40 and opening the chamber 47 r to flow from the chamber 46.- As the detent balls 71 more closely approach the groove 75 the sleeve flange 62 enters the cylindrical body surface 44 to cutoff all flow to the outlet 26b, and all of the fluid under pressure from the inlet end 2611 is diverted to the conduit 50a and cham abutting relation with the ring 67.

During return movement ofthe spool 33 to carry the detent balls 71 from the groove75 to the groove 76, the sleeve 54 remains in abutting relation with the flange and the sleeve 66 is shifted by fluid pressure from the chamber 46 into abutting relation with the spool portion 52 during the initial movement until the-sleeve flange 62 has passed to the right of the cylindrical body surface 44 to allow some ofthe fluid through the inlet 26a to discharge into the outlet 26b. At the same time the spool opening 64 begins to cut ofl the chamber 49 from the discharge passage 29, and completely cuts it off just after the sleeve flange 80, while still abutting. spool portion 52, enters the cylindrical body surface 40. Thereafter the right end of the spool portion 52 enters the cylindrical body surface 40 to cooperate with the sleeve flange 80 in blocking flow from the chamber 46 to the chamber 47.

Leakage from chamber 46 past sleeve flange 80 balances pressures on sleeve 66 and enables spring to thrust the sleeve 66 back into abutting engagement with the clashing with the outer edges of any of the surfaces, The reduced diameter oflsets any slight radial movement of sleeves 54 and 39-45 during shifting of the spool.

66 on the spool 33, and does not affect the efliciency of the valve.

The spool 31 for the single port valve section 18 has a single shiftable sleeve 31 and transverse opening 82,

and the spool 32 of the dual port valve section 19 has a pair of shiftable sleeves 83 and 84 and a transverse opening 85, corresponding to the sleeves 54 and 66 and opening 64 described above, and operating on the same principle.

While I have illustrated and described a presentvpre 'ferred embodiment of the invention it will be understood thatthe invention may be otherwise variously embodied and. practiced within the scope of the following claims.

I" claim:

l'I A valve comprising a case having an opening therethrough, a spool movable lengthwise in said opening, said case'having a passage for fluid under pressure including a circular. valve-seating surface around the pool through which said fluid passes, and said spool having a fixed circular valving flange slidable through said annular surface, the spool being effective to block said passage while the fixed flange is in the annular surface and to free said passage when the spool is shifted to remove the fixed flange from the passage, and a second circular valving flange extending around the spool and slidable along the spool toward and from the fixed flange, the movable flange having a portion adjacent the fixed flange whose diameter is substantially equal to that of the fixed flange and which is slidable through said annular surface, said movable flange forming a continuous valving surface with the fixed flange when the two flanges are together, whereby flow through the annular'passage is variably controllable by compound movement of the spool relative to the case and of the movable flange relative to the fixed flange.

' 2.;A valvecomprising a case having an opening therethrough, a spool movable lengthwise in said opening, said case having a passage for fluid under pressure including a, circular valve-seating surface around the spool through which said fluid passes, and said spool having a fixed circular valving flange slidable through said annular surface, the spool being effective to block said passage while the fixed flange is in the annular surface and to free said passage when the spool is shifted to remove the fixed flange from the passage, a second circular valving flange extending around the spool having a portion whose diameter is substantially equal to the fixed flange slidable toward and from the fixed flange, the movable flange having a portion adjacent the fixed flange whose diameter is substantially equal to that of the fixed flange and which is slidable through said annular surface, said movable flange forming a continuous valving surface with the fixed flange when the two flanges are together, and means yieldably urging the flanges apart, whereby flow through the annular passage is variably controllable by compound movement of the spool relative to the case and of the movable flange relative to the fixed flange as 'a result of fluid pressure and the resilient means acting on the movable flange while the spool is being shifted.

v3. A valve comprising a case and a spool shiftable lengthwise in the case, the case having three chambers around and spaced along the spool with a pair of annular valve-seating surfaces between the central chamber and the respective outer chambers, and the spool having a pair of fixed valving flanges therearound slidable through the respectivel annular surfaces, said fixed flanges being spaced differently from the spacing of the annular surfaces so that only one of the annular surfaces is occupied by oneYof the fixed flanges at any one time, and a third flange slidable lengthwise along the spool to and from one of the'said fixed flanges, said movable flange having a. portion adjacent the fixed flange whose diameter is substantially equal to that of the fixed flange and which is. slidable through one of said annular surfaces, said movable flange forming a continuous valving surface with the said one of the fixed flanges when against the latter flange, said movable flange being shiftable on the spool while the spool is shifted to permit fluid to pass between the central chamber and one of the other chambers at all times, but not between the central chamber andboth of the other chambers at any time.

4. A valve comprising a case and a spool shiftable lengthwise in the case, the case having three chambers around and spaced along the spool with a pair of annular valve-seating surfaces between the central chamber and 8 the respective outer chambers and with different passages connected to the respective chambers for supplying fluid under pressure to one of said chambers, for receiving fluid from. the second chamber, and for passing fluidfrom the third chamber to a fluid-actuated mechanism, and the spool. having a pair of fixed valving flanges therearound slidable through the respective annular sur faces, said fixed flanges being spaced differently from the spacing of the annular surfaces so that only one of the annular surfaces is occupied by one of the fixed flanges at any one time, a third flange having a portion adjacent one of said fixed flanges whose diameter is substantially equal to that of said one fixed flange slidable lengthwise along the spool to and from said one fixed flange, and means yieldably urging the movable flange away from said one of the fixed flanges, said movable flange being slidable through one of said annular surfaces and forming a continuous valving surface with the said one of the fixed flanges when against the latter flange, and said movable flange being shiftable on the spool in response to said means urging it in one direction and fluid pressures urging it in the other direction to permit fluid to pass between the central chamber and one or the other of the outer chambers at all times, but not between the central chamber and both of the outer chambers at any time, during the shifting of the spool.

5. Apparatus according to claim 4 in which a sleeve slidable along the spool has said movable flange projecting around one end thereof, the other end of the sleeve being adapted to engage the other one of the pair of fixed flanges to limit travel of the sleeve toward that fixed flange.

6. Apparatus according to claim 5 in which said yieldable means is a spring between the flanged end of the sleeve and the adjacent fixed flange.

7. Apparatus according to claim 6 in which the flanged end of the sleeve and the adjacent fixed flange each have an annular groove around the spool, said grooves being adapted to receive said spring when the flanged end of the sleeve and the adjacent fixed flange are in abutting relation.

8. A valve comprising a case and a spool shiftable lengthwise in the case, the case having three chambers around and spaced along the spool with a pair of annular valve-seating surfaces between the central chamber and the respective outer chambers and with different passages connected to the respective chambers for supplying fluid under pressure to the central chamber, for receiving fluid from one of the outer chambers, and for passing fluid from the other outer chamber to a fluid-actuated mechanism, and a spool having a pair of fixed valving flanges therearound slidable through the respective an-- nular surfaces, said fixed flanges being spaced further apart than the annular surfaces so that only one of the annular surfaces is engaged by one of the said fixed flanges at any one time, a sleeve slidable lengthwise along the spool between the fixed flanges, said sleeve being of reduced diameter at one end and being of. enlarged diameter at the other end to form a third flange which is slidable through at least one of said annular surfaces and forms an extension of the adjacent fixed flange when against the latter flange, and means yieldably urging the sleeve away from the said one of the fixed flanges, said sleeve being shiftable on the spool in response to said means urging it in one direction and fluid pressures urging it in the other direction to permit fluid to pass between the central chamber and one or the other of the outer chambers at all times, but not between the central chamber and both of the other chambers at any time, during shifting of the spool.

9. A valve comprising a case and a spool shiftable lengthwise in the case, the case having a pair of spaced chambers around the spool and an annular valve-seating surface between the chambers, and the spool having an elongated body portion slidable through said annular surface, one part of said portion being adapted to block a flow between said chambers through said annular surface and an adjacent part of said portion having an opening therein to permit flow of fluid between said chambers along the opening, an end of the opening being curved about an axis transverse to the spool axis for initiating and cutting off said flow gradually as the spool is shifted to connect and disconnect the chambers through the opening, and a circular valving flange having a por tion adjacent the body portion whose diameter is substantially equal to that of the body portion, said circular valving flange extending around the spool and being slidable along the spool toward and away from the body portion, the flange being slidable through the annular surface and forming a continuous valving surface with the body portion when the flange and body portion are brought together.

10. A valve comprising a case and a spool shiftable lengthwise in the case, the case having three spaced chambers around the spool and annular valve-seating surfaces between the chambers, and the spool having an elongated body portion slidable through said annular surfaces, one part of said portion being adapted to block flow between said chambers through said annular sur face and an adjacent part of said portion having a transverse opening therethrough elongated lengthwise of the spool to transmit fluid between two of said chambers when the spool is shifted to bring said opening between two of the chambers, the entering end of the opening passing from one chamber to other being curved for initiating and cutting off said flow gradually as the spool is shifted to connect and disconnect the chambers through the opening, and a circular valving flange at each end of the body portion, said valving flanges each having a portion adjacent the body portion whose diameter is substantially equal to that of the body portion, said flanges extending around the spool and being slidable along the spool toward and away from the body portion, said flanges being slidable through the annular surfaces and forming a continuous valving surface with the body portion when the flange and body portion are brought together.

11. A valve comprising a case and a spool shiftable lengthwise of the case, the case having five chambers around and spaced along the spool, the first being connectible with a source of fluid under pressure, the second being next to the first and adapted to receive fluid under pressure from the first, a third on the other side of the first and connectible with one end of a double-acting cylinder, a fourth connectible to the other end of such double-acting cylinder, and a fifth next to the fourth to receive backflow from said other end of such doubleacting cylinder, said case having a first annular surface between the first and second chambers, 21 second annular surface between the first and third chambers, and a third annular surface between the fourth and fifth chambers, and said spool having three flanges therearound, the first flange being fixed on the spool and slidable through the first annular surface to control flow between the first and second chambers, the second being fixed on the spool and the third being slidable axially along the spool between the first and second flanges, the second and third flanges being slidable through the second annular surface, resilient means urging the movable flange toward the second flange, the movable flange being movable by fluid pressures against said means during shifting of the spool to switch flow from the first chamber away from the second chamber to the third chamber so that there is continuous flow out of the first chamber to the second and third chambers alternately but not simultaneously, and said spool having a portion slidable through the third annular surface with a transverse opening therein elongated axially along the spool to connect the fourth and fifth chambers for discharging backflow when the first chamber is connected to supply fluid to such doubleacting cylinder through the third chamber, said opening being rounded about an axis transverse to the spool axis at the end of the opening which initially connects the fourth and fifth chambers, thereby initiating such flow from the fourth to the fifth chamber gradually as the movable flange is moved on the spool against said resilient means to initiate flow from the first to the third chambers.

12. A spool for a spool valve, said spool having a plurality of fixed valving flanges therearound and spaced axially along the spool, and a movable valving flange adjacent one of said fixed flanges having a portion adjacent to said one fixed flange whose diameter is substantially equal to that of said one fixed flange, said movable flange extending around and slidable lengthwise along the spool, said movable flange forming a continuous valving surface with the fixed flange when the two flanges are together.

13. A spool for a spool valve, said spool having a plurality of fixed valving flanges therearound and spaced axially along the spool, and a sleeve slidable lengthwise along the spool and having a valving flange projecting therearound said valving flange having a portion adjacent to one of said fixed flanges whose diameter is substantially equal to that of said one fixed flange, and forms a continuous valving surface with the said one fixed flange when the sleeve is shifted against said one flange.

14. A spool for a spool valve, said spool having a plurality of fixed valving flanges therearound and spaced axially along the spool, a sleeve slidable lengthwise along the spool and having a valving flange projecting therearound said valving flange having a portion adjacent to one of said fixed flanges whose diameter is substantially equal to that of said one fixed flange, and forms a continuous valving surface with the said one fixed flange when the sleeve is shifted against said one flange, and a spring urging the sleeve away from said one flange.

15. A spool for a spool valve, said spool having a central body portion of uniform relatively large diameter extending along a substantial length of the spool, with a transverse opening in said central body portion elongated axially of the spool and having ends rounded about axes normal to the spool axis, and a pair of sleeves slidable along the spool adjacent the ends of the central body portion, said sleeves each having a flange projecting therearound at one end, said flanges each having a portion adjacent to the body portion of the spool whose diameter is substantially equal to that of the body portion and which forms a continuous valving surface with the body portion when brought into contact therewith.

16. A spool for a spool valve, said spool having a central body portion of uniform relatively large diameter extending along a substantial length of the spool, with a transverse opening through said central body portion elongated axially of the spool and having ends rounded about axes normal to the spool axis, and a pair of sleeves slidable along the spool adjacent the ends of the central body portion, said sleeves each having a flange at its end adjacent the central body, the sleeve flanges forming continuations of the central body portion when the sleeves are against the central body portion, and springs urging the sleeves away from the central body portion.

References Cited in the file of this patent UNITED STATES PATENTS 498,818 Scheid June 6, 1893 1,285,769 Melcher Nov. 26, 1918 2,370,371 Pratt Feb. 27, 1945 2,401,258 Livers May 28, 1946 2,503,827 Langmore Apr. 11, 1950 2,600,702 Stephens June 17, 1952 2,605,108 Stephens July 29, 1952 2,614,503 Berry Oct. 21, 1952 FOREIGN PATENTS 166,619 Great Britain of 1921 

